How do you install a 47 deck belt on John Deere 212 Lawn Mower?

very simple. On the left side of the deck, unlatch the lever on top of the deck, and swing out and to the rear, which will leave the belt tension very loose. Place the new belt on motor pully, and then the rear pully on the deck. Swing the lever back forward and in to relatch it. You're done.